Direct Drive R2

qwertyydude

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Aug 10, 2008
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As you should know from reading my posts, I like direct drive lights. All I have to say is WOW! This thing is insanely bright. It almost rivals my direct drive P7 flashlight, seriously bright. It draws about 2.1 amps off a fresh 18650. So this is definitely not rated for continuous duty seeing as it's only on a Romisen RC-M4. My direct drive P4 module only drew 1.6 amps. But this has to be the king of small form factor flamethrowers with the R2's improved efficiency and lower vF I've got to be pushing close to 350 emitter lumens and more than likely 300+ otf lumens :twothumbs If this thing burns out I'll tell you guys, I'll even try a continuous runtime and report on heat issues. I will definitely put a fan in front to keep from it going :poof:
 

Blindasabat

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Jan 24, 2006
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Have you compared that to the current while direct driving an SSC? I have been direct driving an SSC P4 off of RCR123 and 18650 and have only gotten ~750mA off RCR123 with a lot less off CR123 (60mA!?). I have not measured 18650, but it is not significantly brighter.

I don't have any cree lights running DD yet, but I have an R2 unit on the way that I may have to consider DD in a KX1 head if it will get me similar or better results at lower cost than a driver. May be I can risk a little more light.
 
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qwertyydude

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SSC should be the same because they use cree dies. Try checking your batteries/connections and for me I'm not even running a resistor in series. You may also be overloading those small cells. Lithium ions don't like to be driven at much higher than 1 C.
 

FlashCrazy

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Have you compared that to the current while direct driving an SSC? I have been direct driving an SSC P4 off of RCR123 and 18650 and have only gotten ~750mA off RCR123 with a lot less off CR123 (60mA!?). I have not measured 18650, but it is not significantly brighter.

The Coast Focusing Lensers that I mod and sell are direct drive using SSC USWOH bin, the last letter being the Vf. They typically run around 1000 to 1200 mA off of 3 x AAA NiMH batteries. On an 18650, they hit around 1400. Which bin are you using? Yeah, on a CR123 the voltage is much less than what the LED wants... barely drawing any current there.
 

qwertyydude

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1 update since I was asked more about the light, it's not merely putting direct drive to the pill, the vast amounts of heat generated by the led must be wicked away as fast as possible. This thing will get dangerously hot if left alone. The head gets to 120 degrees in about 3 minutes, meaning my heatsinking job worked. But it will continue to rise if it's not being held, when held it tends to stabilize at about 110 degrees warm but not hot. Runtime is about 1 hour to 50% power, 1 amp in this case, then I get another 40 minutes or so until cell protection kicks in, this is on Trustfire 2400 mah protected cells.

What I did was remove the emitter board because it was glued with what looked to be only silicone caulk, I then cleaned off the glue and sanded the pill machining till it was flat, no ridges. Then I sanded the emitter board till it's sanding marks were gone. This leaves two perfectly flat surfaces. I then used arctic silver epoxy to re-glue the board to the pill making sure to press out any extra glue and air bubbles also filled in the gaps between the board edges and the pill to maximize heat conduction. After this I applied arctic silver heatsink grease to the threads of the pill where it screws into the reflector. To transfer heat to the body I also tightly wrapped, not crumbled, aluminum foil around the reflector so that it completely wedges itself tightly into the bezel, which has the anodizing sanded off the inside to further the heat transfer. And where the bezel screws to the body is sand blasted, with an airbrush sander to remove anodizing, and it is lubed with heatsink grease too.

So just saying this is no simple project since such a high power mod will no doubt fry normal flashlights as probably evident by the posts here with fried high brightness Q5's and P7 flashlights. Strangely enough the 5 mode Aurora P7 flashlight on DX now shows an honest to goodness solid copper heatsink pill, while earlier makes made do with brass, and mine a brass aluminum brass sandwich.
 
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tobjectpascal

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Feb 19, 2006
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I have a Q5 on direct drive after removing the circuit board and replacing the cables with a thicker one to support the extra current.

However, it only pulls 1amp (which is what Cree states it should pull) at 4.2 volts, 2 amps is way way higher than what it should be pulling..

So, does that mean that i have more internal resistance from both the flashlight and internal resistance from the 14500 battery i use? is there less resistance in an 18650 over 14500?

2 Amps should kill an R2. I don't understand why it's pulling that much unless some other resistance is at play feeding as well.

2amps @ 4.2 volts = 8.4 watts, when you consider a P7 is 12.5 watts I can perfectly understand when you say it's almost as bright but i don't understand why it's pulling that much.
 

qwertyydude

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18650's are a very mature technology and I can tell you that a 14500 cannot supply enough current to fully direct drive a power led. Li-ion's cannot supply more than 1 C stably, so you're 800 mah 14500 cell will sag under the current to maybe 3.7 v which is about consistent since it can only reliably output .8 amps.Try measuring voltage at the led, it's tough because while it's on you can't see where to place the leads.

Even on a fully charged 18650 , at two amps, I measure only about 3.9 volts at the actual emitter total powr is 8.19 watts. On my P7 it drops to about 3.8 volts, 2.6 amps so realistically it's only 9.88 watts. Th P7 is still better because I'm overdriving the R2 versus being smack dab in the P7's power range. But the power is awfully close so the P7 only blasts out maybe a couple hundered more lumens. Funny at outputs this high it's hard to discern 200 lumens! :eek:

But normally I'd say 2 amps through a single die will kill it, but judicious planning on my part to remove heat I think is what's making my light survive the torture. No angry blue led after a whole battery cycle, I used a fan to cool it of course.
 
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